The present invention relates to a system and method for monitoring tread wear, shock absorber performance, balance condition of a vehicle tire, and/or rotational speed of a vehicle wheel.
The handling performance of a motor vehicle, e.g., vehicle steering and braking, as well as fuel consumption, is affected by the condition of the tires. Handling performance can be affected by improper tire inflation, abnormal tire wear, out of balance conditions, as well as by poorly performing shock absorbers.
It is estimated that a significant percentage of tires wear out due to abnormal tire tread wear. As a result, over the course of vehicle life, the vehicle would need an additional set of tires, costing additional money. Thus, to save this cost it is desired to alert the driver of abnormal tire wear and other conditions affecting the tires, including improper balance, poorly functioning shock absorbers and improper inflation pressure.
A tire monitoring system currently available from Smartire Systems, Inc. uses wireless technology to monitor the air pressure and temperature in vehicle tires using wireless wheel-mounted sensors and a display receiver mounted within sight and reach of the driver. One sensor is mounted on each wheel and the tire mounted over the sensor, each sensor containing a pressure transducer, a temperature transducer, a centrifugal switch, a radio transmitter and a lithium battery. The display module shows required pressure, actual pressure, pressure status and temperature. While this system provides temperature and pressure information, it does not provide information about tread wear, balance and shock absorber performance.
In addition, anti-lock braking systems (ABS) and integrated vehicle controllers (IVC) require the input of information indicating the wheel rotational speed for each wheel. Currently, a separate wheel speed sensor is provided for each wheel and typically consists of a toothed wheel made of a magnetic disk attached coaxially to a corresponding axle rotatably supporting a tire and a pick-up coil arranged adjacent each toothed wheel with an interval therebetween to provide an alternating sensor signal having a frequency indicative of speed of each tire. It would be desirable to eliminate the need for this type of sensor by using a sensor which also provides additional functions.